Sir James George Frazer (18541941). The Golden Bough. 1922.
religion. At least this appears to be a more probable theory than the opinion, which has found favour with some modern scholars, that Janus was originally nothing but the god of doors. That a deity of his dignity and importance, whom the Romans revered as a god of gods and the father of his people, should have started in life as a humble, though doubtless respectable, doorkeeper appears very unlikely. So lofty an end hardly consorts with so lowly a beginning. It is more probable that the door (janua) got its name from Janus than that he got his name from it. This view is strengthened by a consideration of the word janua itself. The regular word for door is the same in all the languages of the Aryan family from India to Ireland. It is dur in Sanscrit, thura in Greek, tür in German, door in English, dorus in old Irish, and foris in Latin. Yet besides this ordinary name for door, which the Latins shared with all their Aryan brethren, they had also the name janua, to which there is no corresponding term in any Indo-European speech. The word has the appearance of being an adjectival form derived from the noun Janus. I conjecture that it may have been customary to set up an image or symbol of Janus at the principal door of the house in order to place the entrance under the protection of the great god. A door thus guarded might be known as a janua foris, that is, a Januan door, and the phrase might in time be abridged into janua, the noun foris being understood but not expressed. From this to the use of janua to designate a door in general, whether guarded by an image of Janus or not, would be an easy and natural transition.
If there is any truth in this conjecture, it may explain very simply the origin of the double head of Janus, which has so long exercised the ingenuity of mythologists. When it had become customary to guard the entrance of houses and towns by an image of Janus, it might well be deemed necessary to make the sentinel god look both ways, before and behind, at the same time, in order that nothing should escape his vigilant eye. For if the divine watchman always faced in one direction, it is easy to imagine what mischief might have been wrought with impunity behind his back. This explanation of the double-headed Janus at Rome is confirmed by the double-headed idol which the Bush negroes in the interior of Surinam regularly set up as a guardian at the entrance of a village. The idol consists of a block of wood with a human face rudely carved on each side; it stands under a gateway composed of two uprights and a cross-bar. Beside the idol generally lies a white rag intended to keep off the devil; and sometimes there is also a stick which seems to represent a bludgeon or weapon of some sort. Further, from the cross-bar hangs a small log which serves the useful purpose of knocking on the head any evil spirit who might attempt to pass through the gateway. Clearly this double-headed fetish at the gateway of the negro villages in Surinam bears a close resemblance to the double-headed images of Janus which, grasping a stick in one hand and a key in the other, stood sentinel at Roman gates and doorways; and we can hardly doubt that